Quinupristin and dalfopristin are converted to several major active metabolites: 2 conjugated (with glutathione and cysteine) metabolites for quinupristin and one nonconjugated (formed by hydrolysis) metabolite for dalfopristin, which also act synergistically with the complementary parent drug. This conversion occurs in vitro by nonenzymatic reactions independent of cytochrome P-450 (CYP) and glutathione transferase enzymes.
Elevations in serum aminotransferase levels occur in a proportion of patients receiving quinupristin and dalfopristin, but rates are minimally higher than with placebo or comparator drugs. The elevations are generally mild-to-moderate, asymptomatic and self-limited, frequently resolving without discontinuation or even interruption of therapy. Elevations above 5 times ULN occur in less than 1% of patients. Quinupristin-dalfopristin can also cause elevations in direct as well as total bilirubin, but these elevations are mild and not accompanied by elevations in serum enzymes or other evidence of liver injury. In the many clinical trials of quinupristin and dalfopristin there were no instances of clinically apparent liver injury that could be attributed convincingly to their use. Patients who receive quinupristin and dalfopristin are often severely ill, septic and receiving multiple medications or parenteral nutrition, so that jaundice arising during therapy is often multifactorial and difficult to assign to a specific cause. Nevertheless, since the approval and more wide spread use of this antibiotic combination, there have been no published reports of hepatitis or jaundice linked specifically to it use. Thus, clinically apparent liver injury from quinupristin and dalfopristin may occur, but is quite rare.
Concomitant administration of Synercid and nifedipine (repeated oral doses) and midazolam (intravenous bolus dose) in healthy volunteers led to elevated plasma concentrations of these drugs. The Cmax increased by 18% and 14% (median values) and the AUC increased by 44% and 33% for nifedipine and midazolam, respectively.
In vitro drug interaction studies have demonstrated that Synercid significantly inhibits cytochrome P450 3A4 metabolism of cyclosporin A, midazolam, nifedipine and terfenadine. In addition, 24 subjects given Synercid 7.5 mg/kg q8h for 2 days and 300 mg of cyclosporine on day 3 showed an increase of 63% in the AUC of cyclosporine, an increase of 30% in the Cmax of cyclosporine, a 77% increase in the half life of cyclosporine, and, a decrease of 34% in the clearance of cyclosporine. Therapeutic level monitoring of cyclosporine should be performed when cyclosporine must be used concomitantly with Synercid.
A drug interaction between Synercid and digoxin cannot be excluded but is unlikely to occur via CYP3A4 enzyme inhibition. Synercid has shown in vitro activity (MICs of 0.25 ug/mL when tested on two strains) against Eubacterium lentum. Digoxin is metabolized in part by bacteria in the gut and as such, a drug interaction based on Synercid's inhibition of digoxin's gut metabolism (by Eubacterium lentum) may be possible.
A case is presented in which a 21-yr-old woman who was receiving 150 mg/day oral cyclosporine after kidney transplantation developed elevated cyclosporine blood levels 2 days after starting treatment with intravenous injections of 20 mg/kg/day quinupristin/dalfopristin. Baseline trough cyclosporine levels ranged from 80 to 105 ng/ml. Two and 3 days after initiation of quinupristin/dalfopristin therapy, trough cyclosporine levels increased to 261 and 291 ng/ml, respectively. The cyclosporine dosage was decreased to 100 mg/day and the blood levels returned to baseline. After discontinuation of quinupristin/dalfopristin, the cyclosporine blood concentration decreased and the dosage was increased to the previous regimen.
来源:Hazardous Substances Data Bank (HSDB)
吸收、分配和排泄
奎奴普丁和达福普丁在大鼠乳汁中有分布...。
Quinupristin and dalfopristin is distributed into milk in rats ... .
The pharmacokinetics of quinupristin/dalfopristin have been studied in rats, monkeys and humans following intravenous infusion of radiolabelled and unlabelled drug. In rats and monkeys quinupristin and dalfopristin undergo rapid elimination from the blood and wide tissue distribution. Nevertheless, they do not penetrate the central nervous system or cross the placenta to any significant degree and they do not appear to be subject to significant body retention following cessation of administration. The blood elimination half-life of quinupristin was approximately 0.6 hr in rats and 0.5 hr in monkeys, and that of dalfopristin was approximately 0.6 hr and 0.2 hr, respectively. Both compounds are primarily eliminated through the bile into the faeces; quinupristin is mainly excreted unchanged whereas dalfopristin is extensively metabolized beforehand. The metabolites include the microbiologically active pristinamycin PIIA for dalfopristin and the microbiologically active glutathione- and cysteine-conjugated derivatives for quinupristin. Quinupristin and dalfopristin appear to be handled in a similar manner by humans. Following intravenous administration both compounds are rapidly cleared from the blood with elimination half-lives of approximately 1 hr for quinupristin and 0.4-0.5 hr for dalfopristin. The pharmacokinetic profile of quinupristin is dose-independent and so is that of dalfopristin and RP 12536 when considered together. Extravascular diffusion of quinupristin/dalfopristin has been assessed in human non-inflammatory interstitial fluid.
Fecal excretion constitutes the main elimination route for both parent drugs and their metabolites (75 to 77% of dose). Urinary excretion accounts for approximately 15% of the quinupristin and 19% of the dalfopristin dose. Preclinical data in rats have demonstrated that approximately 80% of the dose is excreted in the bile and suggest that in man, biliary excretion is probably the principal route for fecal elimination.
